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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

208

FERRO-ALUMINIUM

In small quantities (0-2%) titanium is often found in ordinary  cast-iron.
The compositions of some of the commoner ferro-titaniums are as follows :

TABLE  XX
Composition of Ferro-titanium

No. j      Fe
	Ti
	c
	Si
	Al
	Mn
	S
	P

I    1   36-85
	56-63
	4-62
	1-25
	0-44
	o-io
	0-045
	O-O2

2      !     78-54
	18-37
	0-67
	1-40
	0-69
	0-18
	0-074
	O-O24

3    I   87-68
	11-21
	0-67
	0-37
	
	
	0-03
	0-04

FERRO -ALUMINIUM

Ferro-aluminium is usually prepared in the electric furnace by reducing
alumina in presence of iron, and serves, like metallic aluminium—which
is much more used at the present time—as a deoxidising agent in the refining
of cast-iron and steel. Its analysis includes :

1. Determination of the Aluminium.—Exact determination of the
aluminium necessitates preliminary expulsion of the iron by exhaustion
with ether in Rothe's apparatus, the aluminium being then precipitated as
phosphate.1 When, however, very exact determination is not required,
the following more rapid method (Regelsberger's) may be followed.

5 grams of the coarsely powdered sample are dissolved in a porcelain
dish in dilute sulphuric acid (1:4), evaporated to dryness and heated on
a sand-bath until white fumes are emitted. When cold the sulphates are
dissolved in hot water and the solution poured into a 300 c.c. measuring
flask, cooled, made up to volume, and filtered through a dry pleated filter
into a dry vessel.

To 100 c.c. of the filtrate sodium bisulphite, or hyposulphite is added
until the iron is completely reduced (a drop of the liquid should give no
colour with thiocyanate), the liquid cooled, most of the free acid neutralised
with sodium carbonate, and the solution poured into a boiling mixture
of 50 c.c. of sodium hydroxide solution (containing 10 grams of sodium
hydroxide) with 40 c.c. of potassium cyanide solution (containing 8 grams
of potassium cyanide).2 When cold, the liquid is introduced into a 500
c.c. measuring flask, made up to volume, and filtered through a dry filter.
To 300 c.c. of the filtrate (= I gram of the alloy), concentrated ammonium
nitrate solution (15 grams in a little water) is added, the liquid being boiled
to expel most of the ammonia, and the precipitated aluminium hydroxide
filtered off, washed until the washing water no longer gives a blue coloration
with ferric chloride, dried, ignited and weighed: A1203 x 0-5303 = Al.

If the ammoniacal solution is heated too long, a little ferric hydroxide
may be precipitated with the aluminium. In this case, the calcined and

1 See A. Ledebur : Leitfaden fur Eisenhutten Laboratorien, gth edition, p. 153.
3 If the reduction were not complete, small quantities .of iron and manganese might
be precipitated as hydroxides.           .         •                                                   .....d